1. Field of the Invention
The present invention relates to an apparatus that controls the transport of a chemical stimuli or drug to a particular location. In particular, it relates to an apparatus that accurately controls the concentration of the supply of the chemical stimuli or drug to a location with the concentration of the chemical stimuli or drug being known at each and every point in time through an improved culture chamber wherein the desired concentration is developed.
2. Description of the Prior Art
The maintenance of biological tissue, such as organs isolated from the natural nutrient supply is of great importance. A significant amount of research has been done with regard to organs that have been removed from their natural bodies. The research is quite varied and ranges from simply trying to keep the particular organ alive outside of the body, to studying the complex responses to the isolated organ to various chemical stimuli.
One successful apparatus that administers a chemical stimuli or drug such that its concentration is known at each and every point in time is manufactured under the trademark of ACUSYST 100. The ACUSYST 100 is manufactured by Endotronics, Inc. of Minnesota, which is the assignee of the present invention. The ACUSYST 100 is described in a patent application having Ser. No. 388,136 entitled "Apparatus for Delivering a Controlled Dosage of a Chemical Substance," filed on June 14, 1982. In the ACUSYST 100, the chemical stimuli or drug is delivered into an airtight chamber wherein the volume is kept constant in order to determine the concentration of the chemical stimuli or drug within the chamber. The volume of the chamber is occupied partially by fluid and partially by air. However, due to the gasified nature of the medium in the chamber, further accumulation of gas ocassionally results in the chamber. It has been found that the volume in the chamber fluctuates slightly on ocassion due to temperature and atmospheric pressure fluctuations causing gas accumulation which results in pressure fluctuations. The pressure fluctuations expand and contract the volume of gas within the chamber which distorts the known volume of the medium in the chamber which in turn affects the calculation of the concentration of the chemical stimuli or drug within the chamber.
Although the inaccuracies that may result from a temperature and pressure fluctuation in the chamber are small, constant fluctuations have a cumulative effect in controlling the desired concentration of the chemical stimuli or drug within the chamber.